Chapter 3 - Fuel System Components Adn Operation Flashcards
Fuel is stored in tanks which can be :
Integral
Metal
Flexible fabric membrane
Fuel tank pressure requirement
Unpressurised iron pressurised with air
Effect of altitude increase
Atmospheric air pressure decrease and boiling point of all liquids decreases
Purpose of tank pressurisation and vent system
Maintain the pressure of air above the fuel at an appropriate level
Air/ No fuel valve use
Prevents loss of fuel during inverted flight or AC climb
Pressurised tanks advantages
Can transfer fuel between tanks
Prevents excessive fuel vapour
Reduces fire risk
Maintains shape of flexible tanks
Pressurised tanks disadvantage
Added weight and routing complexity of additional components and pipework
Tank pressurisation system components
NRV
PRV
Outward relief valve
Inward relief valve
Fuel/No air valve
Vent valve
Pressure switch
Fuel supply components
Booster pumps
NRV
Low Pressure (LP) Fuel Filter
LP Fuel Cock
Fuel cooled oil cooler (FCOC)
Surface type heat exchanger
Temp increase of fuel will prevent any water it may hold from turning to ice which could block the supply line
Air Cooled Fuel Cooler (ACFC)
Cools fuel to prevent vapour locks and gum residues forming
Ejector (jet pump)
Used with or alternatively to ACFCs - cool hot fuel by mixing with cold fuel prior to its return to a fuel tank
Methods of fuel transfer
Air pressure
Electric transfer
Fuel ejectors
Gravity
Air pressure transfer
Increasing pressure in a tank producing a force on the surface of the fuel that is used to push it through transfer pipelines to the next tank
Electric Transfer pumps
Similar to booster pumps, fitted in pairs with a NRV on the outlet of each pump to prevent fuel being recirculated back into the tank if one pump fails
Fuel ejectors (jet pumps)
Uses a small amount of fuel from the booster pump outlet directed to the fuel ejector nozzle
Components for fuel tank level and transfer control
Float valve
Float switch
Float valve
No electrical input, sense and control the transfer by automatically stopping flow when a specific level is reached
Float switch
Positioned to sense a specific level and complete an electrical circuit, signal is then passed to fuel control system which controls tank level by sending signal to open or close valves or turn on or off pumps
Purpose of fuel management and control
Maintain CG by managing transfer sequence
Provide indications of various parameters and warnings of malfunctions
Give crew various options in the movement of fuel and to counter any system malfunctions
Methods of achieving control (automatically)
System design/layout
Electrical components
Mechanical components
Fuel flow proportioners
Used to maintain balance by taking a specific amount of fuel from two or more sources and passing it to a common outlet
Pipelines
Join various components in the aircraft systems to permit fluid flow between them.
Fuel content purpose
To provide a continuous and accurate indication to the crew of the quantity of useable fuel on board
List of indications given by fuel gauging system
Total fuel systems contents
Contents of individual tanks or group of tanks
Amount of fuel being used at any given time
